. >> reporter: connecticut senators richard blumenthal and chris murphy are cosponsoring the bill. they say the shooting at sandy hook elementary school in newtown, connecticut proves there's a need to bran assault weapons. >> newton -- to ban assault weapons. >> newton changed things. >> reporter: but the nra says law abiding citizens need the same technology criminals have. >> we have the right to defend ourselves and our families with semiautomatic firearms technology. >> reporter: the nra has a lot of support here on capitol hill, especially in the house where many say an assault weapons ban has little chance of being passed. >> this is going to be a tough go. >> reporter: it may be tough to win over some of the public as well. on wednesday, sheriffs in missouri, california, and texas announced they would not enforce new gun control laws such as an assault weapons ban. that i feel and can prove that are unconstitutional, we will not enforce those. >> reporter: president obama is sending vice president biden on the road to gather public support. >> we're growing to take it to th